Tanning



further object to "tion 'and r and containing at I 'cycloaliphatic Patented Mar. 16, 1943 UNITED STATES PATENT OFFICE- TANNING Paul R. Austin and William EwLundquist, Wii-- mingto notation of Delaware I No Drawing. Application October-.6, 1941, .Serial No. 413,834

22 Claims.

chain substituent on the ring and containing at least one carbon-'to-carbon double bond which may be either a part of the cycloaliphatic annular structure or in the open-chain substituent on the n i ere have recently been developed tanning processes which involve the use of an acidic polymeric material in which the acidity is due to assignors to E; I. du Pont de & Company, Wilmington, bet, a cormay be a product or reaction of materials comprising maleic anhydride and a cyclic terpene.

These products may desirablybe used alone or in conjunction with the tanning agents specifically pentene, alpha-pinene,

carboxyl groups attached to aliphatic carbon atoms. These processes-are described in the George D. Graves Patents 2,205,882 and 2,205,883.

These tanning agents are sometimes used with foam depressants as described in the Joseph, S. Kirk Patent'2220,867 and skins tanned'with these agents are desirably affected by treatment with a metal salt asdescribed in the Joseph S. Kirk Patent 2,205,901. a

It is an'object of this invention to produce tanning compositions and processes which are economical and whichlead to leather of improved character. It is a further object to provide tanning compositions and processes by means of which there may be produced leather of good fullness, mellowness and smooth grain characteristics. It is a still further object to produce imin the George D. Graves patents above mentioned and further described in the said Joseph provide tanning compositions whichmay'advantageously be used in conjuncwith the agents of the said patents to George D. Graves and Joseph .Sl Kirk. It is a still further object of this invention to particularly white leather of improved character and color. Further objects will become apparent hereinafter.

action of materials comprising maleic" anhydride and. an unsaturated wcloaliphatic hydrocarbon having a six-membered cycloaliphatic'ring with at least one opm-chainsubstituent on ring' least onecarbon-to-carbon double bond which may be either 'a part of the annular structure orin the opens. Kirk patents. It is a stilt present purposes we proved tanning compositions and processes ofthe 5 p ter described chain substituent on described in the said Graves and. Kirk patents. Or better yet, there may be employed a polymerization product of maleic anhydride with both a material with which it will polymerize as in the Graves Patent 2205;882 and with a cyclic terpene. The'cyclic terpenes which are of the most interest for tanning compositions of the present invention are those commercially available from the naval stores industry, for instance, dipentene, alpha-pinene, beta-pinen camphene, alphaterpinene, phelandrene, and terpinolene. Di-

and alpha-terpinene are of particular interest because they are plentiful The terpenes have the and readily available. molecular formula CioHmAand contain one or two double bonds per molecule.

be used in the pure state but as a practical matter it will usually be found expedient to use commercial mixtures obtained by fractionation of wood turpentine. Cheap terpene by-products consisting of a wide range of CmHm terpenes, as for example the mixture of terpenes formed as a by-product from the rearrangement of alphapinene to camphene,

have found that excellent results are obtained which is composed largely of and is called; dipentene.

While it is preferred, as above indicated, to

use a terpene there may be used any unsaturated cycloaliphatic hydrocarbon having a six-membered cycloaliphatic the ring andcontaining at least one carbon-to-carbon double bond which may be either a part of the cycloaliphatic annular structure or in the open-chain substituent on the ring. Other such compounds, for instance,

produce leather The foreioing and other objects of this inven tion are attained by the use of a product of rechain substituent on the ring. Preferably there so are vinyl cyclohexene, methylene cyclohexane.

- Terpene reaction vinyl cyclohexane; and

025; Peterson 3993,1131; and Humphrey 2,1 18,925.

While terpene-maleic anhydride reaction products such as those of the Peterson and Humphrey patents may-advan The terpenes may are alsolsuitable. For our using'a commercial fraction ring with at least one openportionwhichihaathemoat according to the present from this thereaction can bon is attached L: zLis hydrogen or a hydrocarbon beneficial effect. One may recover and employ the high molecular weight portions of the reaction product, say by extraction of the less def sirable portion with ether.

" Dipen'tene-maleic anhydride reaction productsor the high molecular weight polymeric fraction of .said reaction products may advantageously be used as assistants to tanning agents of the Graves and Kirk patents before mentioned and they may be used either simultaneously or one before the other in either order. It may be found desirable, for instance, to make a mixture of dipentenemaleic anhydride reaction product with a tanning composition of any of the examples of Graves 2,205,882, say with styrene-maleic anhydride interpolymer of Example 5.

When a terpene maleic anhydride reaction product is to be' used with a product of the said Graves or Kirk patents which itself includes maleic anhydride there is great advantage in polymerizing both products simultaneously.

I When a terpene is polymerized with maleic anhydride in the presence of another polymerizable material which exothermically pelymerizes with the maleic anhydride and which contains a vinyl, vinylene or vinylidene group the yield of high molecular weight or polymeric terpene-polymer is much greater. The resulting product is far more eflicient as a tanning agent than a mere mixture of the individual reaction products and the leather producible is of superior quality. It will be understood that polymeric tanning agents pared by including a terpene in the polymerization of maleic anhydride with any polymerizable material as suggested in the aforesaid Graves and Kirk patents. Additional maleic anhydride equivalent to the terpene should be used but aside be carried out very much as in the aforesaid Graves and Kirk patents.

While any polymerizable material, as set out in the aforesaid Graves and Kirk patents, may

be used with maleic anhydride and a terpene as group by not more than one ato the remaining valences of the group in which a. carbon atom joined to bond, the carbon atom -cH =c and which radical are satisfied by hydrogen or hydrocarbon radicals. By formula these compounds deflnedas polymerizable mono-olefinic organic compounds having the formula may be Y I v radicaL' invention may be pre- I X is hydrogen or a hydrocarbon radical, and Y is an organic radical containing a carbon atom joined to another atom by a plural bond, said carbon atom being removed from the ZCH=C radical by not more than one atom. Z and Y may be connected. In the preferred compounds Y is an aromatic hydrocarbon radical, for example as in styrene and indene. Typical of these compounds are vinyl esters, ethers, ketones, e. g. vinyl acetate, vinyl phenyl ethers, ketone, aryl vinyl compounds wherein the vinyl group is attached directly to nuclear carbons, e. g., styrene; aryl vinylene compounds wherein the vinyl group is attached directly to the nuclear carbon, e. g., indene; alpha-methylene aliphatic monocarboxylic acids, their esters, amides and nitriles, for example, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, methacrylamide, methacrylonitrile, acrylonitrile, and the like. Of these the preferred compounds are styrene and indene and their alkyl substitution products.

The polymerization of tanning agents of the present invention may be carried out as in the aferementioned Graves and Kirk patents using .any of various well known procedures such as elevated temperatures with a catalyst and in the presence those effected at benzoyl peroxide as of solvent or dispersion media such as acetone,

' tioned benzene,

. C. may be employed but the rate of reaction 6 generally becomes very toluene, or those carried out by heating in the absence of a solvent and in the presence or absence of a catalyst orv by exposure \to ultraviolet light.

- While excellent yields areobtained with socalled bulk polymerization, products of more desirable character may ordinarily be prepared by dissolving the reactants in a suitable. solvent. Materials suitable for use as solvents should preferably boilat, say C. or above, be inert to maleicanhydride and the product. Among such solvents may be mentoluene, xylene, higher alkylated benzenes, dioxan, acetone, and methyl ethyl ketone. Commercial styrene is frequently supplied to the trade in 50 to 60 per cent of xylene and when using such styrene it will ordinarily be desirable to use the xylene already present as the solvent. It will ordinarily be found desirable not to use a great excess of solvent over that required and the use of a higher proportion of solvents than about 50 per cent based on the total weight of the reaction mixture is usually not advantageous for economic reasons.

While as above indicated, polymerization may be effected. in numerous ways and may use a catalyst, for instance such as ultraviolet light, it is ordinarily preferred to-use a eroxide. Peroxides which may serve as catalysts are organicsoluble peroxides which include benzoyl peroxide,

acetyi peroxide, butyryl peroxide,- lau.royl peroxide, succinoyl peroxide, and ascaridole. Benzoyl peroxide, the preferred catalyst, is generally ,at temperatures of from about C. to the boiling point of the reaction mixture which is usually'below 175 C. Temperatures below 80 I slow. as the temperature is decreased. when the reaction is carried out at C. or above it is usually complete in onehourorless.

In preparin polymerization products using maleiczanhydride' methyl vinyl the other materials to. be polymerized, and be readily separated from with both a cyclic terpene and another material polymerizable with the maleic anhydride the molecular proportion of reactants is frequently chosen so that the moles of maleic anhydr'lde equal the sum of the moles-of terpene plus the moles of the second polymerizable material. An excess of terpene may sometimes be used to advantage. The molar ratio of maleic anhydride terpene :polymerizable vinyl, vinylene or vinylidene compound may vary from say 16:l5:l to 2:1;1. Preferred tanning agents will have a ratio say from 4:3,:1 to'2:1:l. The ratio of reactants to be employed varies with the type of product desired; for example, maleic anhydride dipentene styrene copolymers prepared from a 2:1:1 reaction mixture are of higher average molecular weight than copolymers prepared from a 4:3:1 reaction mixture. Inasmuch as the commercial terpenes are generally cheaper than the second material polymerizable with maleic anhydride it is ordinarily desirable to use as high a proportionof terpene in the reaction mixture as possible and still obtain a tanning agent of required character. According to a preferred practice of the invention polymers of good character may be obtained'using from 20 to 60 per cent of a cyclic terpene, to per cent of maleic anhydride, and 5 to 30 per cent of vinyl, vinylene, or vinylidene compound, the total components equaling 100 per cent by weight ratio. 1

After polymerization has been completed the reaction mixture may be extracted with ether or benzene to isolate thepolymeric product. The

' polymeric product may also be. recovered by digesting the reaction mixture with aqueous caus- 5 tic whereupon all acidic products will pass into solution in theaqueous layer and may be separated from the oily layer consisting of solvent, small amounts of unreacted starting material,

Polymeric tanning agents for use according to the present invention 'should be soluble in alkaline solutions at the pH at which tanning is 1' to be started. It is also to be observed that while best results are obtained with toohigh for reasons pointed out inthe aforesaid Graves and Kirk paten The of this invention may be used for the treatment of any-type of skin adapted 50 to be converted into leather or fur. It is to be observed that the term "skin is used generically to include heavy skins such as cowhide, lighter skins such as goatskin and calfskin, and

also skins of fur-bearing animals. It will nato5,

urally be necessary to adapt the processes to the type of skin to betreated. For instance,

' goatskin'may be more rapidly tanned'than calfskin, but those skilled in the art are well aware of such factors and may readily adapt the agents of this invention to thespecific needs of particular specialized problems. Skins to be tanned according to the processes pickled. The skins may if desiredbe depickled. They may also be given a salt liquortreatment to soften them up and to render them of more uniform conditon as is the practice in prior art tanning processes. V V While skins prepared in any manner may be treated according to the processes of this invention, the pH of the skins is important. As will .be observed below, the tanning is effected at cerpolymeric 45 'materials the molecular weight should not be .willbefo a tain conditions of acidity and the skins may tend to change these conditions. The'tanning solution may suitably be controlled to compensate for any variance of the pH of theskins from that of the tanning solution. It may sometimes be found advantageous to adapt the processes for preparing the skins so that a skin prepared for tanning is approximately at the pH of the tanning solution.

Too rapid reaction. of the tanningagent withthe skin in the first stages of the process should be avoided in order to prevent surface hardening of the skin. In tanning with acidic polymeric tanning agents this result is accomplished by careful adjustment of the pH of the tanning solution. The exact acidity of a tanning solution containing a polymer according to this inventanning solution initially at a pH from about 4.7

to 5.0. sun more specifically, it will be found 5 that under many conditions of operation a pH ofabout 4.75 is optimum. Ata pH much below 4.7 the afllnity of skins for the polymerization products becomes so great that surface hardening takes place, while at a pH much above 4.7 the 30. afllnity of the hides for the tanning agent is so decreased that penetration rapid for the best results. c

The acidity of the polymerization products may suitably be adjusted by the use of such alkalies as alkali metal hydroxides or carbonates, am-' monlum hydroxide, and organic bases such as ethanolamines. As has been observed before, the pH of the hide should be considered in adjusting is not sufllciently the pH of the tanning solution so that the 1 and so forth. 4o

ity a suitable buffer salt such as sodium acetate or sodium phosphate may be included in the tanning solution.

After satisfactory penetration of skins by the tanning agent has been effected the rate of tanning may be accelerated by lowering the pH of the solution. The pH to which the solution should be brought to eflect complete tanning will vary considerably with the specific typeof skin being treated. It will not generally be desirable to go to a pH belpw about pH 3 since,at a higher hydrogen ion concentration, hydrolysis. of the skinzmay take place. As a practical matter it d that the pH should be lowered to about 3.4 to 4.2, while more specifically it will be found thatin many processes a pH of about 4 will be most satisfactory. V

.'1'he lowering of the pH of the tanning solution may suitably be effected by the-use of any acidic material such-as lactic, hydrochloric, sulfuric, acetic, phosphoric, sulfamic, and formic I H The considerations as to the type of apparatus to use; the time to be allowed for tanning, the,- temperatures of tanning, and the amounts of tanning agent'are substantially thosej known to the art in connection with prior art tanning proc- .esses. The time allowed for tanning must be sufllcient to permit complete penetration of the tanning agent and the pH should not be lowered too rapidly or there maybe puckering and apparent over-tonnage of the grain surface. The tanning can best be effected at room temperataken up by the leather'in a reasonable period 7 of time.

After askin has been tanned with a. polymeric material it is then preferably treated with a. salt of a metal selected from. the group consisting of aluminum, iron, titanium, copper, zirconium, and chromium. The treatment isefiected by subjecting the leather to the action of a solution of the metal salt, the treatment being continued long enough to assure penetration of the hide by the metal salt solution.

While any soluble salt such as the sulfate, chloride, lactate, or acetate of aluminum, iron, titanium, copper, zirconium, or chromium may be used, it is preferred to use salts of inorganic acids, particularly those whichare neither strongly oxidizing nor reducing. More specifically, it is preferred to use a salt of an acid selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, and sulfamic acid, and by far tfh: best results have been obtained with the 5111- a BS.

The polymers employed for tanning skin according to the present invention apparently form some kind of chemical complex with skins and it is believed that the leather produced according .to methods of this invention comprises a reaction product of skin substance with a polymeric prodnot of reaction of materials comprising a cyclic terpene and maleic anhydride.

It will be understood that polymers of the present invention may if desired be used together with other tanning agents or tanning assistants in manners known to the art. They may, for instance, be used in conjunction with vegetable tanning materials such as quebracho extract,

with chrome tans, or with synthetic tanning agents containing sulfonic acid groups. The tanning assistants used in conjunction with the acidic polymers may be used simultaneously or may precede or follow the treatment with the polymer; After skins have been tanned according to processes as above outlined it will often be found desirable also to treat with an aldehyde such as formaldehyde using for this purpose, 2 to 5 per cent commercial formalin (40 per cent skins;

' HCHO) on the original dry pickled weight of the v Tanning compositions according to the present invention may advantageously contain a foam. depressing material such as octanol as described particularly in the aforesaid Joseph S. Kirk-Patent 2,220,867. V v

It will often be found desirable to eflect taming "and subsequent treatment with metal salts, ifused, in the presence of surface-active agents of the type'often used as fat-liquoring assistants; Particularly excellent results have been obtained use of a soluble lactate, acetate, citrate, or tartrate or by using lactic, acetic, tartaric or citric acids themselves.

The leatherobtained according to the preferred processes of this invention is white but it may if desired be treated with white pigment or may be colored during or after the tanning process by the inclusion of any of the common leather dyes and filled or given any of the numerous surface treatments customary in the art.

In order that the invention may be better understood reference should be had to the following illustrative examples:

EXAMPLEI Preparation of tanning agent Sixty-eight parts by weight of commercial dipentene, 98 parts of maleic anhydride, and 46.5'

parts of 56 per cent styrene were mixed and heated to 100 C. Polymerization was induced by the addition of one part of :benzoyl peroxide and the temperature of the reaction mixture rose to 155 ('J. When it had cooled to C. 3.5 parts of catalyst dissolved in 46.5 parts of '56 per cent styrene was added slowly to the well-stirred reaction mixture at such a rate as to maintain the reaction temperature between 140 and ter the reaction had subsided the crude product was treated with 40 parts of sodium hydroxide in abouta thousand parts of water. The mixture was warmed until solution of the polymer was complete. The organic layer consisting of xylene and unreacted dipentene was separated from the The aqueous solution of hydrolyzed polymer. final aqueous solution was at a pH of 5.2 and contained about 14. per cent of polymer as the anhydride or 17 per cent of polymer expressed as thepartial sodium salt of the hydrolyzed polymer.

Tanning process Preparatory to tanning parts by weight of drained pickled calfskin which had been previously limed and bated in customary manner,

were placed in a tanning receptacle to which there cent of the drained pickled weight of skins. The

skins were agitatedin this solution for five minutes in order to depickle partially and to prepare them for tannage.

A tanning solution, was prepared by adding 0.5 part by weight of octanol to'73 parts by weight of a solution of polymer at pH 5.2 prepared as above outlined. I 1

The tanning solution was added to the receptacle which contained skins and depickling liquor in three approximately equal portions at fifteen-minuteintervals. The skinswere agitated using chlorosulfonated straight chain hydrocarbons, the treatment tending to improve the quality of the leather and having no deleterious action on the resistance of the leather to ultraviolet light.

The treatment with a metal salt, if used, may

' frequently .be modified to advantage by the joint between additions and after the 'last addition were agitated for one hour. The pH of the solution at the endof this time was 4.78.

' The pH of the tanning solutionwas then lowered to. 3.5'by' the addition of dilute sulfuric acid (10 per cent H2804). Ten parts by weight of the dilute acid was added and this addition was amazes repeated each half hour until four additions had been madeand the desired pH had been reached. The'total time required for the addition was two hours and after this the agitation was continued for twenty minutes. The skins were now tanned and had a soft, full, well-tanned feel.

To the skins in the now exhausted tanning liquor was added 102 parts by weight of a per cent water solution of aluminum sulfate (A1z(SO4)a-18H:0) which was prepared by dissolving 100 parts by weight of aluminum sulfate in 1000 parts by weight of water. The agitation was continued for fifteen minutes without interruption. To the solution containing the tanned skins and alum solution was then added 3.4 parts by weight of sodium acetate and the agitation continued for fifteen-minutes.

The solution was then neutralized to pH 5.03 by the addition of a 10 per cent solution of sodium bicarbonate during the course of one hour and fifty-five. minutes of agitation. The bicar- .5 part by weight of octanol. This solution was added to the tanning receptacle in three substantially equal portions and the receptacle is agitated for fifteen minutes between each addition. Agitation was then continued for one hour withggt interruption and a pH was finally reached of' 4.

The pH of the tanning, solution was adjusted to 3.41 by the addition of a dilute sulfuric acid solution as in Example I. At the end of this treatment the skins had assumed a full tanned eel. To the taming receptacle containing the tanned skins and exhausted tanning liquor was then added 109 parts by weight of a 10 per cent aluminum sulfate solution prepared as in Example I. The receptacle and contents were agi-.

. tated for fifteen minutes and then 3.6 parts by bonate solution was added in four approximately equal portionswith twenty-minute intervals of agitation betw'een'additions. About twelve parts by weight of sodium bicarbonate were used.

The tanned leather was piled down over night,

shaved, washed thoroughly to remove salts, and

fatliquored. The leather was hung to dry, sammied, staked and tacked out flat. The leather was found to be extremely full, white, and mellow and had outstanding quality.

Exuirnn II Preparation of tanning agent One hundred two parts of commercial dipentene and 98 parts of maleic anhydride were heated to 120 C. A solution of 3 parts of benzoyl peroxide in 46.5 parts of 56 per cent styrene was added slowly to the reaction mixture at such a rate as to maintain the reaction temperature at remainder of the product was hydrolyzed with alkali and waterand the organic layer consistweight of sodium acetate wa added. Agitation was continued for fifteen minutes- The solution 7 was then neutralized to pH 5.05 by successive additions of a 10 per cent solution of sodium bicarbonate. The additions were made at twenty minute intervals using five additions of about 25 parts by weight of solution each. The total quantity of bicarbonate used was about 12.5 parts by weight and the total time for neutralization was one hour and fifty-five minutes.

The skins were then piled down over night and on the following day washed, shaved, and fatliquored. They were then dried, sammied, staked and tacked- The resultant leather was white, full, mellow, and of extremely-desirable quality.

EXAMPLE III Preparation of tanning agent A ter'pene-maleic anhydride polymer prepared with maleic anhydride and alpha-terpinene as in Peterson and Littmann Patent 1,993,025 was extracted with a large volume of ether. About 3 per cent of the total weight was isolated as a ing of xylene and unreacted dipentene was removed. The solution obtained was at a pH of 5.2 and contained 11.8 per cent of polymer expressed as the anhydride, or, equivalently, 14.6

per cent of polymer expressed as the partial sodium salt of hydrolyzed polymer.

Tanning process For tanning there was taken 182 parts by weight of drained, pickled calfskin which had been previously limed, unhaired, and bated. The

drained pickled weight of skin. The skins were agitated in this solution for five minutes in order to effect a partial depickling of the skins.

A tanning solution was prepared taking '93 parts byweight of the solution of partially neutralized polymer prepared as above, diluting with iii-parts by weight' of water, and adding thereto solid product. This solid product was dissolved in dilute alkali to produce a 10 per cent solution (based on anhydride) as pH 5.2. Forty parts by weight of this solutionwas used with parts by weight of a 10 percent solution of' a styrene-maleic anhydride polymer of pH 5.2 prepared as in Example II of the aforementioned Kirk Patent 2,205,901.

' Tanning process v Two hundred parts by weight of drained picv kled calfskin which had been previously limed and bated were placed in a tanning receptacle which contained a solution of sodium chloride and sodium acetate in water. This solution contained 15 parts by weight of sodium chloride which corresponds to 7.5 per cent of the drained pickled weight of skins. Ten grams of sodium acetate which corresponds to 5per cent of the drained pickled weight and 250 parts by weight of water which corresponds to .125 per cent of the drained pickled weight. of skins The tan- The pH of the solution was then lowered to 3.50 by the addition of 10 per cent sulfuric acid solution. The acid was added in four portions: of 10 parts by weight each with a final addition of 6 parts by weight. A total of about 46 parts by weight of dilute acid was used and the acidi- -of a per cent solution o Neutralization was co ficatien required two hours and twenty-five minutes.

The skins now had a plump, tanned appearance.

To the receptacle containing the skins and exhausted tanning liquor was added 160 parts by weight of a 10 per cent aluminum sulfate solution and the receptacle was agitated for :flf-

teen minutes. Four parts by weight of sodium acetate was then added and the receptacle was agitated for another fifteen minutes. The solution'was then neutralized to pH 5.0 by seven stuccessive additions of 10 per cent sodium bicarbonate at intervals ofpabout twenty minutes durirg which time the skins were agitated continuously. There was used a total of about 145 ,parts by weight of 10 per cent solution and the a small initial exothermic reaction has subsided,

8 parts of benzoyl peroxide is added slowly to the reaction mixture with constant stirring at such a rate as to maintainthe reaction temperature between 125 and 150 C. The yield of benzene-insoluble polymeric product amounts to 213 parts or 47 per cent of the total weight of reactants. A portion of this was hydrolyzed with aqueous alkali to obtain a clear solution having a pH of 5.2 and containing 10 per cent of the polymer based on the unhydroiyzed anhydride.

Tanning process One hundred fifteen parts by weight of drained pickled calfskin were placed in a tanning receptacle with a solution of sodium chloride and sodium acetate in water as in Example I using the same proportion of solution based on the drained pickled weight. After five minutes of agitation there was added to the receptacle in three equal portions and at fifteen-minute intervals a tanning solution containing 92 parts by weight of the 10 per cent aqueous solution of polymer prepared as above.

The skins were drummed for one and onehalf hours and were then acidifiedto pH 3.5 by the addition of 10 per cent sulfuric acid. The

additions were made at twenty-minute intervals using five parts by'weight of acid at each'addition; The total acid usedamounted to 30 parts by weight of 10 percent H2804 solution and the acidification required two hours and ten minutes.

The skips were soft, mellow, and appeared well tanned.

To the tanning receptacle containing the tanned skins and exhausted tanning liquors was added 92'parts by weight of a 10' per cent solution of aluminum sulfate, and the receptacle was agitated for one-hal f hour.'.

ditions of sodium bicarbonate solution at twenty-minute intervals until a total of five additions had been made. The total time was two hours and ten minutes. and the final pH reached was 5.1.

The resultant leather was washed and fatliquored as in Example I to'produce a leather which was soft, full, and white.

EXAMPLE V Preparation of tanning agent Forty and five-tenths grams of vinyl cyclohexene, 49 parts of maleic anhydride, and 23.2 parts of 56 per cent styrene were dissolved in 450 parts of xylene. and 2 parts of benzoyl peroxide was added. The mixture was heated until polymerization began at 85-90" C. The temperature remained at 100--110 for an hour during the polymerization. The product was isolated by filtration and amounted to 60 parts. A portion of it was hydro lyzed with aqueous alkali to obtain a solution having a pH of 5.2 and a concentration of 10 per cent basedon the unhydrolyzed polymer.

Tanning process 1 As in Example I, 180 parts by weight of drained, pickled calfskin were treated with a solution of sodium chloride and sodium acetate.

To 108 parts by weight of a tanning agent prepared as above there was added 0.5 part by weight of octanol and the mixture was added to the tanning'receptacle in three-equal parts at intervals of fifteen minutes. After addition agitation of the skins was continued for an hour, reaching a pH finally of 4.83.

The pH of the tanning solution was lowered to 3.55 by adding 10 per cent sulfuric acid in four portions each amounting to about ten parts by weight and each addition being made after about thirty minutes agitation. The total time of acidification was one hour and fifty minutes and the final pH was 3.55. The leather produced had a To the receptacle was added 2.3 parts by weight of sodium acetate a elf-20 parts by weight dium bicarbonate.

tinue by successive ad- 'vals over a total time of two hours tacked out fiat.

full tanned feel and appearance.

The leather produced as above was left in the exhausted tanning liquor and there was added 108 parts by weight of a 10 per cent solution of aluminum sulfate (A12(SO4) 3.18H2O). The solution was agitated for fifteen minutes afterwhich 3.6 parts by weight (which is 2 per cent of the drained pickled weight of the skins) of sodium acetate was added and agitation was continued for another fifteen minutes. The solution was then neutralized to pH 5.03 with sodium bicarbonate. The additions' were made at interminutes.

The skins were piled down over night after which they were washed, shaved, and fatliquored. The skins were then dried, sammied, staked and The resulting product was a white leather which was well-tanned and exhibited good leather characteristics.

EXAMPLE VI Preparation of tanning agent Forty-nine parts of maleic anhydride and 48 parts of methylene cyclohexane were dissolved in 250. parts of dioxan and 1 part of benzoyl peroxide catalyst was added.- The solution was heated on a steambath for one hour during which time it gradually became more viscous.

After cooling the polymeric product was isolated by running the dioxan solution slowly into The solution .was warmed and five I a well-stirred '50:!50' mixture of water and methanol. A portion of the polymeric material I thus obtained was hydrolyzed by digestion with dilute alkali to obtain a solution having a pH of 5.2 and a concentration of per cent based on the unhydrolyzed polymer. 1

Tanning P706888 Ninety-five parts by weight of a tanning sold-1 tion prepared as above and containing 0.5 part by weight of octanol were used for tanning 158 parts by weight of calfskin using a process as described in the foregoing example. The leather produced was extremely full, white, soft, and

supple. Exmrts VII Preparation of tanning agent Thirty-four parts of beta-pinene and 24% parts of maleic anhydride were heated to 95 C.

in a reaction vessel provided with a stirrer and a reflux condenser and 1 part of benzoyl peroxide was added slowly with stirring. The heat of the reaction caused the temperature to rise gradually to ,160 C. When the reaction temperature began to subside an additional part of benzoyl peroxide'was added. After cooling, the

reaction mixture was extracted with ether to remove unreacted monomenand low molecular weight polymeric products. The yield of ether insolubleproduct was 34 parts or 58 per cent of the weight of the reactants. This material was dissolved in aqueous alkali to obtain a solution for use in tanning. r

Tanning process Tanning was effected as in the previous examples with 129 parts by weight (drained pickled weight) of calfskin which after depickling was added to 77.4 parts by weight of a 10 per cent solution of the product prepared as above.

EXAMPLE VIII Preparation of tanning agent rial w'hich precipitated out was isolated by filter ing and drying. The yield was 61 parts or52 per cent of the weight of the reactants.

. Tanning process Tanning was effected substantially as in the preceding examples with the product thus prepared.

EXAMPLE IX Preparation of tanning agent Fifty-one parts of beta-pinene, 49 parts of maleic anhydride, 13 parts of styrene, and '10 parts of xylene are heated on a steam bath to 90 C. Two-tenths partoflbenzoyl peroxide is then added and the temperature very slowly and smoothly rises to around C; After'cooling, the product is extracted withaether to obtain 91 parts of ether-insoluble, product which One and one-half part of reaction mixture.

polymeric product amounts to,l01 parts or 48 the low-boiling vinyl acetate.

is equivalent to 81 actants.

, Tanning process The product of this example was used for tanning in the manner previously shown.

EXAMPLE. X Preparation of tanning agent- Thirty-six parts of methylene cyclohexane, 49

parts of maleic anhydride and 13 partsof toluene were dissolved in parts of xylene and the solu tion was heated to 90 C. in a reaction vessel provided with a stirrer and a reflux condenser. One

part of benzoyl peroxide was added. The heat" of polymerization caused the temper'atureto rise to135 C. After cooling, the xylene insoluble product was isolated and dried. The yield was 77 parts or 79 per cent of the weight of reactants.

Tanning process The product was used as a tanning assistant in a manner similar to that of the preceding ex- ExAMPL'n XI Preparation of tanning agent Sixty-eight parts of dipentene and 98 parts of maleic anhydride are heated to C. A'solution of 4 parts of benzoyl peroxide in 43 parts of vinyl acetate is added slowly to the reaction mixture which is kept under reflux to avoid loss of Then an additional part of peroxide catalyst is'added to the The yield of ether-insoluble per cent of the weight ofthe reactants.

Tanning process The tanning agent obtained was used in tanning processes such as those previously described.

Exaurm XII Preparation of tanning agent One hundred two parts of the commercial terpene fraction boiling at 1'75-187 C. and 98 parts of maleic anhydride are heated to C. A solution of 4 parts of benzoylperoxide in 26 parts of styrene and 26 parts of xylene is then added slowlyto the reaction mixture at such a rate as to maintain the reaction temperature at 130-140 C. At the end of the reaction an additional onehalf part of benzoyl peroxide catalyst is added. After cooling the product is extracted with ether to obtain 147 parts of ether-insoluble polymericproduct which .is equivalent to a 65 per cent yield based on the total weight of reactants.

Tanning process A tanning solution was made up using one per cent by weight of the productthus prepared together with 5 per cent of a styrene-maleic anhydride polymer prepared as in Example II of Kirk Patent ,2,205,901. The tanning solution was used as previously described.

Tanning compositions of the present invention may most desirably be offered to the trade as partial sodium salts ofa polymeric reaction product of materials comprising a cyclic terpene and maleic anhydride, and it will customarily be found desirable for these compositions to dissolve in water to give a tanning solution ofpH from about 4.8 to 5.7. L If desired, however, unneutralized polymer may) be sold-to the trade and it may be adjusted to a suitable pH prior to tan-.

ning.- Tanning compositions of the invention per cent of the weight of retive processes and compositions it will be understood that without departing from the spirit of thi invention one skilled in the art may readily devise numerous tanning solutions, compositions,

and processes employing products of reaction of materials comprising a cyclic terpene and maleic anhydride.

We claim: 1. In a process for the treating of skins, the step comprising subjecting a skin to the action of a product of reaction of materials comprising maleic anhydride and an unsaturated aliphatic cycloaliphatic hydrocarbon having a six-membered cycloaliphatic ring with at least one openchain substituent on the ring and containing at least one 'carbon-to-carbon double bond which may be either a part of the cycloaliphatic annular structure or in the open-chain substituent onthe ring, 7 v 2. In a process for the treating of skins, the step comprising subjecting a skin to the action of a polymeric product of reaction of materials comprising maleic anhydride and a cyclic ter-' 3. In a process for the treating of skins, the

step comprising subjecting a skin to the action of a polymerization product of maleic anhydride with a cyclic terpene and with another material with which it will polymerize.

4. In a process for the tanning of skins, the step comprising subjecting a skin to the action ot a polymerization product of maleic anhydride with a polymerizable vinyl, vinylene, or vinylidene merization product of maleic anhydride with a cyclic terpene and with another material with which it will polymerize.

12. A. tanning composition comprising a polypound and with a cyclic terpene.

14. A tanning composition comprising a polymerization product of maleic anhydride with a cyclic terpene and styrene.

, 15. A tanning composition comprising a polymerization product of maleic anhydride with dipentene and styrene.

16. Leather which comprises a reaction product of skin substance with a product of reaction of materials comprising maleic anhydride and an unsaturated cycloaliphatic hydrocarbon having a six-membered cycloaliphatic ring with at least one open-chain substituent on the ring and containing at least one carbon-to-carbon double bond which may be either a part of the cyclobe either a part of the cycloaliphatic annularstructure or in the open-chain substituent on the ring.

5. In a process for the step comprising subjecting a skin to the action of a polymerization product of maleic anhydride with a cyclic terpene and with a polymerizable vinyl, vinylene, or vinylidene compound.

6. In a process for the tanning 0f skins, the step comprising subjecting askin to the action of a polymerization product of maleic anhydride with a cyclic terpene and styrene.

7. In a process for the tanning of skins, the step comprisingsubjecting' a skin to the action of a polymerization product of maleic anhydride with dipentene and styrene.

8. A composition for treating skins comprising a product 'of reaction of.materials comprising maleic anhydride and a cyclic terpene.

9. A composition in treating skins comprising a partially neutralized acidic polymerization product of reaction of materials comprising -maleic anhydride and a cyclic terpene, the.com-;

position upon dissolving in water .forming a solution with a pH of about 4.8 to 5.7. v p

110. A composition for treating skins comprising a polymeric product of reaction of materials comprising maleic anhydride and a cyclic terpene.

.11. A tanning composition comprising a polytanning of skins, the

aliphatic annular structure or in the open-chain substituent on the ring.

17. Leather which comprises a reaction product of skin substance with a polymeric product of reaction of materials comprising maleic anhydride and a cyclic terpene.

18. Leather which comprises a reaction prodnot of skin substance with a polymerization proddouble bond which may be either a part of the cycloaliphatic annular structure or in the openchain'substituent on the ring.

20. Leather which comprises. a reaction produuct of skin substance with a polymerization product of maleic anhydride with a polymerizable compound selected from the group consisting of vinyl, vinylene, and vinylidene compounds and with a cyclic terpene.

21. Leather which comprises a reaction product of skin substance with a polymerization productlof maleic anhydride with a cyclic terpene and styrene.

22. Leather which comprises a reaction productof skin substance with a polymerization prod uct of maleic anhydride with dipentene and styrene.

PAUL R. AUSTIN.

, WILLIAM E. LUNDQUIST. 

